Immunogenetic categorization of lymphocytes into sets and subsets separately programmed for coordinate expression of surface phenotype and function is crucial to much current immunologic research. Definition of the Ly123, Ly1 and Ly23 sets is only a beginning. Much formal investigation will be needed for even a bare description of the immune system in these new terms, because a single new system like Qa-1 can geometrically increase the details to be unraveled. This grant renewal application centers on immunogenetic aspects and is geared to collaborative studies that should be particularly rewarding in this formative phase of the field. Technical additions to this laboratory, since the preceding award, are a unit for assay of immune functions in vitro and another for monoclonal antibody production by hybridomas, both now fully operational. In addition to maintenance and expansion of our antiserum bank and tumor panel, the work outlined concerns: (a) Definition of new alloantigenic systems; unique features of the Ly-9 and "U" (Qa-Tla region) systems are stressed. (b) Production of congenic mice for high potential systems. (c) Genetic linkage; the unmapped Ly-9 and Pca-1 loci head our list. (d) Phenotyping of cell sets in developmental sequence; with current emphasis on the Qa-1 plus and Qa-1 minus lineages. (e) Phenotyping of cooperative cell sets; with current emphasis on whether and how Lyl:Qa-1 plus and Lyl:Qa-1 minus sets collaborate in, and mediate, help. (f) Regulation; illustratted in the phenotyping of cell sets mediating feedback suppression of antibody production. (g) Selective T cell reconstitution of B mice; its evaluation as a general method for defining the ontogenetic rank and potential of defined cell sets. (h) Evaluation of flow cytometry and sorting for standardized particular applications; in collaboration with the Laboratory of Investigative Cytology. (i) Applications of hybridoma technology for monoclonal antibodies.